The object of the present invention is a pyrotechnic composition for delay elements incorporated in time fuses, for example, which is based on metallic antimony and potassium permanganate. The composition is used mainly in time fuses which are to have delay intervals of 150 milliseconds (ms) and up.
As is known, time fuses are used where explosive charges are to be detonated successively, at predetermined defined time intervals, by a single ignition. The time interval from the start of initiation of ignition to detonation of the time fuse is termed delay time.
To secure optimum effectiveness of time fuses, the delay time must be maintained as accurately as possible. The unavoidable variation in delay time must be so small that the burning time of a given time stage is not shorter than the longest burning time of the next-lower time stage and not longer than the shortest burning time of the next-higher time stage. This means that there must be no overlapping of the burning times of adjacent time stages.
The difference between the delay times of adjacent time stages of time fuses is known as delay interval. Thus, time fuses having delay intervals of 500 ms in time stage 3 should detonate 1500 ms after initiation of ignition, and those of time stage 4 should detonate 2000 ms after initiation of ignition.
It is further known to use mixtures of metallic antimony and potassium permanganate in delay compositions with time intervals of one-half second and up. However, there is so much variation in these compositions that they result in overlapping in the interval range below 500 ms.
Thus, there has been a need for pyrotechnic composition which has so little burning-time variation even with delay intervals of 150 ms and up that no overlapping occurs when it is used in time fuses.